The preparation and use of magnetically responsive beads are known in the art. See. e.g., U.S. Pat. Nos. 4,285,819, 4,582,622, 4,795,698, 5,091,206, 5,795,470, 5,648,124, and 5,834,121. Carbon beads have been used as HPLC packing materials and coating filler. Quantum dots have found their applications in bioanalysis just recently. Quantum dot nanocrystals are nanometer scale particles that are neither small molecules nor bulk solids. Their composition and small size (a few hundred to a few thousand atoms) give these dots extraordinary optical properties, which can be readily customized by changing the size or composition of the dots. This property is the basis for encoding using quantum dots.
Microarray, biochips, and high throughput bioassays have experienced rapid progress during last several years. There are two types of biochips: passive and active biochips. Passive biochips refer to those on which chemical or biochemical reactions are dependent on passive diffusion of sample molecules. Active biochips, on the other hand, allow versatile functions of molecular manipulation, interaction, hybridization reaction and separation by external forces through means such as microfluidic manipulation and electrical manipulation of molecules. When functional beads are used as molecular carrier, the beads are manipulated on the active chips.
Although beads technology has found wide applications in separation and analysis, there is a limited supply of various beads, especially those suitable to be used with active biochips, e.g., multiple-forces chips. The present invention addresses this and other related needs in the art.